1. Field of the Invention
This invention relates t a helical scan digital data reproduction apparatus, and particularly relates to a helical scan digital data reproduction apparatus suited for a digital audio tape recorder and a PCM audio VTR.
2. Description of the Prior Art
A digital audio tape recorder (DAT) in the form of a helical scan digital reproduction apparatus is known which can record a digital audio signal on a magnetic tape. In such a digital audio tape recorder, searching for a desired program is carried out by using an index signal, a program number, or a START-ID code. The index signal is recorded on a longitudinal track at the beginning of a program to indicate a start timing of a program. The program number is recorded at a predetermined portion of a helically scanned track in an ID-code form to indicate an ordinal number of one of a plurality of programs and is recorded at a beginning of the program if there is no interval between the preceding program and the following program, or recorded at a beginning of the interval if there is the interval. The START-ID is recorded at a predetermined portion of a helically scanned track in the ID-code form at a beginning of a program. The index signal can be detected during rewinding, fast-forwarding, and high speed reproducing modes because it is reproduced from the longitudinal track by a fixed head. On the other hand, the program number and the START-ID cannot be detected during rewinding, fast-forwarding, and high speed reproducing modes because they are reproduced by rotary heads. The START-ID is used in the DAT while, in a PCM audio VTR, a program start flag is used. The program start flag corresponds to the START-ID and is also recorded at a predetermined portion of a helically scanned track in the ID-code form at a beginning of a program and also cannot be detected during rewinding, fast-forwarding, and high speed reproducing modes because they are reproduced by rotary heads.
When an index signal is used, a prior art digital audio tape recorder can search for a desired program data in accordance with a manually inputted ordinal number indicating a distance from the present tape position. This type of index search is a relative search, because the input ordinal number indicates a relationship to the present tape position. However, such a recorder cannot perform absolute searching wherein a program is located according to a single program number indicating an ordinal number relationship with respect to the beginning of the magnetic tape.
An absolute search is possible when program numbers represented by ID codes are used. However, in the PCM audio VTR it is difficult to read out the ID code except in a program reproduction mode. Therefore, the ID code cannot be used in a search mode when the recording medium is being wound or rewound at a high speed (fast forward or rewind modes).
Moreover, if a user inputs program number to be searched, it is impossible to search for a program if the program number of the present position of the tape has not been detected, for example just after placing the cassette in the digital audio tape recorder.
This invention is developed to overcome the above-mentioned problem and to perform absolute searching according to the program number in modes other than the program reproduction mode.